The latent nutritional values present in many vegetables, particularly the oilseed vegetables such as soybeans and other legumes and cottonseeds, is well known. Utilization of these nutrient sources has been severely hampered, however, by the presence in these vegetable nutrients of naturally occurring substances that interfere with their digestibility and palatability. The principal deficiencies of vegetable nutrient sources are their typical beany flavor and their poor digestibility. The beany flavor, particularly when used as an animal feed can often be overcome by cooking or toasting. However, the poor digestibility of vegetable nutrients, such as soy protein, is caused by the presence of oligosaccharide sugars and additional antinutritional factors, such as trypsin inhibitor and proteins that show antigenicity. Finally, since these crude feedstock materials are products of the agricultural and food processing industries, their consistency and/or quality can be variable.
The oligosaccharide sugars are considered to be antinutritional factors, because they can cause flatulence. This flatulence typically results in discomfort, diarrhea, loss of appetite, poor growth, and in the case of young animals can even result in death. These effects have in part been responsible for the lack of wide-scale use of vegetable nutrients as milk replacements for human and animal consumption.
Antigenic proteins present in oilseeds are believed to interfere with or slow down the growth rate of young animals. The antigenic factors are generally associated with the presence of glycinin, betaconglycinin, lectin and urease that occur naturally in vegetable nutrients such as soy beans and cottonseed. In young animals, the presence of these substances typically results in diarrhea, poor growth and may even lead to mortality.
Vegetable nutrients such as oilseed based products and soy products, in particular, also typically contain factors which inhibit the natural digestive action of the trypsin enzyme in the intestine. While these trypsin inhibiting factors may be reduced to lower levels by heat treatment, such heat treatments are not always effective or desirable.